This looks like an urgent personal matter.
I would like to think, given the choice, they'd stick with the better (but clearly less lucrative) tour.. but the situation doesn't really appear to be about that choice. It's just bad timing.
Onto an unrelated matter, the most disappointing thing about letlive is their tour choices. They seem to be a legit band that wants to be taken seriously, but then they'll go out on a tour with Falling in Reverse. It gives you a (good) reason to question them. Thankfully (and confusingly), they also get on quality tours like ETID/TC and Underoath/mwY/ACB.
They're tight with Enter Shikari, and knowing the dudes, they're not all about playing to a certain type of crowd so that's likely why they took that FIR tour.
Really hope everything's alright on their end though.